46 MORPHOLOGY AND EVOLUTION The intraparietal sulcus may be bifid posteriorly, the posterior limbs forming the transverse occipital sulcus (T.O.S.). The latter is situated behind the parieto-occipital sulcus and in front of the simian sulcus tS.S.); in many Anthropoid Apes the two latter are concurrent. The posterior rhinal fissure is nearer the mesial surface than in the Lerouroidea. The cerebellum is relatively larger transversely than in the Lemuroidea, and different brains exhibit varying degrees in the size of the flocculi and paraflocculi. The latter form the petrosal lobules. Owing to the increased bulk of the cerebellum the paraflocculi are reduced. The trapezium is concealed.